1. Field of the Invention
The present invention relates to the field of cryptography. More specifically, the present invention relates to the robustness of stream ciphers.
2. Background Information
Crytographic ciphers can be broadly divided into block ciphers and stream ciphers. Block ciphers cipher a block of plain text into ciphered text by applying multiple successive rounds of transformation to the plain text, using a cipher key. An example of a block cipher is the well known DES cipher. Stream ciphers cipher a stream of plain data into ciphered data by combining the stream of plain data with a pseudo random sequence dynamically generated using a cipher key. An example of a stream cipher is the well known XPD/KPD cipher.
Conventionally, if an application requires block as well as stream ciphering, both ciphers are provided. For hardware implementations, this is inefficient and wastes valuable real estate space. Accordingly, a dual use block/stream cipher that can be used as either block cipher or a stream cipher is desired.